1. Field of the Invention
The present invention relates to an inline type check valve for use in a hydraulic circuit, and more particularly to a check valve provided with an umbrella-shaped piston which is quick in response.
2. Description of the Prior Art
As is known, an inline type check valve comprises a tubular body made of metal press-fitted in a hydraulic circuit, inlet and outlet formed at opposite ends of the body, a steel ball or poppet axially, movably mounted in the body, a coil spring mounted behind the ball or poppet in the body to force the ball or poppet against an annular seat surrounding the inlet, and a snap ring removably fixed to the body to back up the coil spring.
The known valve has disadvantages when used in an oil circuit. It is somewhat slow in response. The reason for this is that the ball is massive and less responsive and the poppet makes cylindrical contact with the inner periphery of the body and, therefore, is less responsive. A metallic contact between the seat and the ball or poppet offers no perfect sealing and allows oil leakage through the valve. In assembly, skill is required for the snap ring to be set against the coil spring in the body. It is costly to produce the metallic body within a desired tolerance. Besides, it can not increase the rate of flow without enlarging the diameter, because the rate depends on an annular clearance between the inner diameter of the body and the outer diameter of the ball or poppet.